This invention relates to a gearbox assembly for vehicles applicable, particularly, to motorcycles, motorized tricycles, scooters or automobiles of a bar handle type designed for use off-road or on rough roads.
Conventional vehicles for rough road and field use are, generally, equipped with an engine and a gearbox similar to those of a highway motorcycle. However, because a large driving torque, which is required to get out of depressions, cannot be obtained from such a gearbox, it has become desirable to obtain the required driving torque by treating the conventional gearbox as a main gearbox, adding a sub gearbox and providing gear-shifting to a low speed in the sub gearbox. It is also desired to provide the feature of backward motion with a reversing gear. In the above, though a reversing transmission system can be incorporated in the main gearbox, this requires a nearly complete redesign of the main gearbox. Futher, because the main gearbox undergoes frequent gear shifting operation though pedal manipulation, incorporation of the reversing system into the main gearbox produces operational problems.
Further, the sub gearbox is usually mounted at a displaced position relative to the main gearbox, so it is unnecessary to adjust the width of the vehicle frame and to pay attention in designing the position of a foot-rest step relative to the gearboxes.